Can I do more than ctrl z/ go back very far into my model?
Blender saves one (by default) backup version of the file when you save it. You can look in it (it's named whatever.blend1) to see if it has the version you want.

Also, Blender also saves a backup file as you work, every 2 minutes by default. You can use File > Recover Auto Save... to restore this and see if it has the version you want.

If neither of these work, you are probably out of luck this time. There are a few things you can do to keep it from happening again, though:


Increase the Undo Levels in Editing preferences, so you can go back farther. I use 256 myself, but you may want to try less if it makes you run out of memory.
Increase the number of .blendX backup files Blender makes, in File preferences. I use 32, but this may be too many for you.


After changing any settings, remember to press the Save User Settings button! Otherwise, your changes will not be saved.